Multiple sound frequency inlet silencer



Aug. 27, 1957 J. N. HELLER ET AL 2,804,161

MULTIPLE scum) FREQUENCY INLET SILENCEIR Fi led Nov. 16, 1953 5 Sheets-Sheet 1 Aug. 27, 1957 J. N. HELLER ET AL 2,304,161

MULTIPLE SOUND FREQUENCY INLET SILENCER Filed Nov. 16, 1955 3 Sheets-Sheet 2 AT TQRNEY Aug. 27, 1957 J. N. HELLER ETAL 2,804,161

MULTIPLE SOUND FREQUENCY INLET SILENCER Filed Nov. 16. 1953 3 Sheets-Sheet 3 ATTORNEY United States Patent MULTIPLE SOUND FREQUENCY INLET SILENCER Joseph N. Heller and Robert H. Spahr, Jr., Flint, Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application November 16, 1953, Serial No. 392,088

14 Claims. (Cl. 181-35) This invention relates to silencer devices and has particular relation to silencer devices especially applicable for use with the induction systems of internal combustion engines or other devices for automotive and other uses.

In constructing silencers it has been the practice heretofore to provide a resonating chamber and an acoustical coupling means for sounds of a single wave length or in a single frequency band to be transmitted by a sound transmitting passage. Inasmuch as most sound transmitting passages employed in the working fluid systems of engines or other devices transmit sounds of more than one frequency or in more than one frequency band it has been necessary heretofore either to employ a plurality of resonating chambers and acoustical coupling means each tuned to a sound of diiferent frequency or in a different frequency band in the sound transmitting passage or to employ a single resonating chamber and acoustical coupling means for attenuating the most objectionable sound inthe sound transmitting passage. Other sounds either were not silenced by the device or they were attenuated or absorbed by sound absorbing material, hiss chamber means, filter means or other expensive and more or less ineifective devices.

It has been discovered that it is possible to tune a single resonating chamber to "sounds of different frequency that may be transmitted by sound transmitting passage means. This may be done by providing a resonating chamber of predetermined acoustical capacitance, then connecting the chamber to the sound transmitting passage through a plurality of acoustical coupling means of different inertance values. In such construction the resonating chamber and each acoustical coupling means may be tuned to the Wave length of different sounds in the sound transmitting passage and all of the sounds that may be transmitted by the passage may be attenuated by a single silencer device.

In the drawing:

Figure 1 is a side elevational view with parts broken away and shown in cross section, of a cleaner silencer assembly embodying the principles of the invention;

Figures 2 and 3 are views similar to Figure l, of other cleaner silencer assembly structures embracing the principles of the invention.

Figure 4 is a side elevational view of an internal combustion engine of a type now generally employed for automotive and other uses and equipped with a cleaner silencer structure embracing the principles of the inven tion.

Figure 4 illustrates an engine having a fuel and air induction system 11 which may be, supplied with air by a cleaner silencer assembly 12 similar to the cleaner silencer structures 13, 14 and 16 shown by Figures 1 to 3.

The cleaner silencer assembly structures 13, 14 and 16 may include air cleaner devices 17, 18 and 19 respectively for cleaning the air supplied to the induction system 11 of the engine 10. The assemblies 13, 14 and 16 also may include silencer devices 21, 22 and 23 respectively 2,804,161 Patented Aug. 2 7, 1957 for attenuating sounds created in the engine 10 and transmitted to the cleaner silencer assemblies 13, 14 and 16 through sound transmitting passages 24, 26 and 27. It will be apparent that the sound transmitting passages 24, 26 and 27 may terminate beyond the silencer devices 21, 22 and 23 respectively, in the event the cleaning devices 17, 18 and 19 are not employed. In the present instance the sound transmitting passages 24, 26 and 27 include air collecting chambers 28, 29 and 31 respectively, filter unit passages 32, 33 and 34 respectively, oil supply chambers 36, 37 and 38 respectively and annular cleaner inlet passages 39, 41 and 42. The sound transmitting passages 24, 26 and 27 also convey the air supplied to the engine through the cleaner silencer devices 13, 14 and 16, respective'ly.

Within the silencer devices 21, 22 and 23 the sound transmitting passages 24, 26 and 27 may be formed in any suitable manner as by the employment of telescoping conduits indicated at 43, 44 and 46, 47, and 48, 49, respectively.

1n the structure disclosed by Figure l the silencer device 21 is formed to provide a resonating chamber 51 having a predetermined acoustical capacitance value suitable for attenuating sounds of different frequency created in the engine 10 and transmitted through the sound transmitting passage 24.

The resonating chamber 51 may be acoustically c0upled with the sound transmitting passage 24 in any suitable manner as by an elongated annular passage 52 formed between the telescoping conduits 43 and 44 and by opening means of different cross sectional area indicated at 53 and 54 and extending through the conduit 43 at different distances from the end of the conduit 44. The elongated annular passage 52 opens into the sound transmitting passage 24 toward the inlet to the conduit 43 which is adapted to be connected to the induction system of the engine by any suitable means indicated at 56. It will be apparent that the passage 52 and the opening means 53 and 54 form unrestricted sound transmitting coupling passage means of low acoustical impedance and between the sound transmitting passage 24 and the resonating chamber 51. One of such passage means includes the two openings 53 and the outer end of the passage 52, the other of which includes the passage 52 and the opening means 54. The two passage means illustrated have different acoustical inertance values, the inertance value of the latter being greater than that of the passage means involving the openings 53 and the end of the passage 52.

It will be apparent that sounds in different frequency bands created in the engine and transmitted to the outer end ofthe sound transmitting passage 24 may be attenuated by the two acoustical coupling means and the resonating chamber 51. This may be done by properly relating the inertance value of the coupling means pro vided by the openings 53 and the end of the passage 52 to the acoustical capacitance value of the resonating chamber 51 to sounds in a single frequency band transmitted by the passage 24 and by properly relating the inertance value of the acoustical coupling means provided, by the passage 52 and the opening means 54 to the acoustical capacitance value of the chamber 51 and sounds in a difierent frequency band in the sound transmitting passage 24.

The silencer 22 disclosed by Figure 2 may be assumed to include a resonating chamber 57 having a predetermined acoustical capacitance suitable for attenuating sounds of different frequencies that may enter the sound transmitting passage 26.' The resonating chamber 57 is acoustically coupled to the sound transmitting passage 26 through opening means 58 in the conduit 46, through openings 61 in the conduit 47 and the part of the annular.

passage 59 between the opening means ing means 61. The resonating chamber 57 also is acoustically coupled to the sound transmitting passage 26, through the opening means 58 and the length of the annular passage 59 between the opening means 58 and the end of the conduit 47.

It will be apparent that the opening means 58 is of greater cross sectional area than the opening means 61 although this area relationship of the openings is not essential to the operation of the device. It will be further apparent that the inertance value of the acoustical coupling means comprising the full length of the passage 59 and the opening means 58 is greater than the inertance value of the acoustical coupling means comprising the opening 61, the intermediate part of the passage 59 and the opening means 58.

Sounds of different Wave length in the sound transmitting passage 26 may be attenuated by properly relating the inertance value of the coupling including the passage 59 and the opening means 58 and the acoustical 58 and the open- H capacitance of the resonating chamber 57 to the wave length of sounds of a single frequency or a single frequency band and by properly relating the inertance value of the coupling means including the openings 61, the intermediate part of the passage 59 and the opening means 58 and the capacitance value of the resonating chamber 57 to the Wave length of sounds of a diiferent frequency or a different frequency band.

The sounds in such different frequency bands may be created in the engine 10 and transmitted to the sound transmitting passage 26 which is connected to the induction system 11 of the engine by coupling means 62.

In the structure disclosed by Figure 3 the silencer 23 is formed to provide a resonating chamber 63 of a predetermined acoustical capacitance value suitable for attenuating sounds of more than one wave length that may be supplied to the sound transmitting passage 27 extending through the structure. The chamber 63 may communicate with the sound transmitting passage 27 through low impedance acoustical coupling means including the opening means 64, the Width of the elongated annular passage 66 between the conduits 48 and 49 and the opening means 67 formed in the conduit 49. The chamber 63 also may communicate with the sound transmitting passage 27 through the low impedance acoustical coupling means provided by the opening means 64 and the outer end of the elongated annular passage 66.

It will be apparent that the opening means 64 is of greater cross sectional area than the opening means 67 although this area relationship of the openings is not essential to the operation of the device. It will also be apparent that the inertance value of the acoustical coupling formed by the opening means 67 and the opening means 64 which are directly opposed to one another across an intermediate part of the passage 66 is less than the acoustical inertance value of the coupling means provided by the passage 66 and the opening means 64.

The silencer 23 may be made to attenuate sound of different frequencies that may be transmitted to the passage 27 by properly relating the inertance value of the coupling means provided by the opening 6'7 and the opening means 64 and the capacitance value of the resonating chamber 63 to the Wave length of a sound of a single frequency or a single frequency band and by properly relating the inertance value of the coupling means provided by the passage 66 and the opening means 64 and the acoustical capacitance of the resonating chamber 63 to the Wave length of a sound of a different frequency or a different frequency band.

Such sounds of different wave lengths may be created in the engine 10 and transmitted to the passage 27 by the engine induction means 11 which may be connected to the silencer 23 by means indicated at 68.

[The silencer 23 also is formed to provide a second resonating chamber 69 which is acoustically coupled to the sound transmitting passage 27 through opening means 71 and the lower extremity of the passage 66 for attenuating sounds of still other frequencies or frequency bands that may be created in the engine 10 and transmitted to the sound transmitting passage 27.

The claims:

1. A silencer device having sound transmitting passage means formed therein and extending therethrough and adapted to transmit different sounds at the same time and to be connected to means for simultaneously creating said different sounds and for transmitting said sounds to said sound transmitting passage means, a resonating chamber having an acoustical capacitance of predetermined value and formed in said device, and a plurality of acoustical coupling means having diiferent inertance values and providing impedance means connecting said sound transmitting passage means to said resonating chamber, said acoustical capacitance value of said resonating chamber and said difierent inertance values of said coupling means being the values that tune said resonating chamber and said coupling means to the Wave lengths of said different sounds and that attenuate said different sounds when said sound transmitting passage means is connected to said means for creating said different sounds.

2. A silencer device as defined by claim 1 and in which said low impedance acoustical coupling means comprises openings of different size between said sound transmitting passage means and said resonating chamber.

3. A silencer device as defined by claim 1 and in which said low impedance acoustical coupling means includes a pair of telescoping conduits also forming part of said sound transmitting passage means extending through said device.

4. A silencer device as defined by claim 1 and in which said low impedance acoustical coupling means includes opening means of different cross sectional area and disposed in parallel relation to one another and between said resonating chamber and said sound transmitting passage means.

5. A silencer device as defined by claim 1 and in which said low impedance acoustical coupling means includes opening means of different cross sectional area arranged in series between said resonating chamber and said sound transmitting passage means.

6. A silencer device as defined by claim 1 and in which said low impedance acoustical coupling means comprises an elongated annular passage connecting said sound transmitting passage means to said resonating chamber and through opening means of different cross sectional areas.

7. A silencer device as defined by claim 1 and in which said low impedance acoustical coupling means connecting said sound transmitting passage to said resonating chamber includes an elongated passage connected to said sound transmitting passage and said resonating chamber by opening means having dilferent cross sectional areas.

8. A silencer device as defined by claim 1 and in which said low impedance acoustical coupling means connecting said sound transmitting passage means to said resonating chamber includes elongated passage means of different lengths.

9. A silencer device as defined by claim 1 and in which said low impedance acoustical coupling means connecting said sound transmitting passage means to said resonating chamber includes elongated passage means of diiferent cross sectional areas.

10. A silencer device as defined by claim 1 and in which said low impedance acoustical coupling means connecting said sound transmitting passage means to said resonating chamber includes parallel passage means of different lengths.

11. A silencer device as defined by claim 1 and in which said low impedance acoustical coupling means connecting said sound transmitting passage means to said resonating chamber includes parallel passage means of different cross sectional areas.

12. A silencer device as defined by claim 1 and in which said sound transmitting passage means and said resonating chamber are defined as silencer means and in which said low impedance acoustical coupling means is formed to provide elongated passage means connected to one of said silencer means by openings of different cross sectional areas.

13. A silencer device as defined by claim 1 and in which said low impedance acoustical coupling means is formed to provide passage means of ditferent inertance values and extending in series between said resonating chamber and said sound transmitting passage means.

14. A silencing device for automotive vehicles and for other purposes and having a sound transmitting passage formed therein and adapted to simultaneously transmit sounds of different frequencies and having a resonating chamber formed therein large enough to be capable of being tuned to sounds in said transmitting passage of said 6 different frequencies, acoustical coupling means formed in said device between said sound transmitting passage and said resonating chamber and having the sound transmitting capacity to tune said resonating chamber to the sounds in said sound transmitting passage of one frequency, and another acoustical coupling means formed in said device between said sound transmitting passage and said resonating chamber and having the sound transmitting capacity to tune said resonating chamber to sounds in said sound transmitting passage of another frequency.

References Cited in the tile of this patent UNITED STATES PATENTS Nulty Mar. 31, 1936 Sebok June 15, 1954 OTHER REFERENCES 

